1. Field of the Invention
This invention relates to a camera using a film cartridge provided with rotatable display means rotatable with a supply spool in the film cartridge and displaying by its rotated position whether the film is unused or used, and rotation restraining means for preventing said supply spool from being rotated except during the loading with the camera.
2. Related Background Art
A film cartridge designed such that whether the film therein is unused or used is displayed by a member movable in response to the rotation of a supply spool in the film cartridge is proposed in Japanese Laid-Open Patent Application No. 2-114248.
In the above-described example of the prior art, it is necessary that a member for locking the rotation of the supply spool be provided in the film cartridge to prevent the supply spool from being inadvertently rotated to thereby change the display, that is, to prevent the occurrence of the deviation of the relative position of the member movable with the supply spool and (the outer cover of) the film cartridge, when the film cartridge is removed from the camera and is a single piece.
Accordingly, to load the camera with the film cartridge and start the feeding of the film, said lock member must be released.
However, the film twines around the supply spool and therefore, tension is created in the direction of rotation of the supply spool and thus, the supply spool is rotated upon unlocking and the relative position of the member movable with the supply spool and (the outer cover of) the film cartridge is changed, and this has led to the possibility of displaying wrong information. Particularly when the information as to whether the film is unused one or used one is changed by mistake, it will result in a serious error such as double exposure.